Farm dams are an ever-present feature in any rural landscape in Australia and worldwide, but they also emit extremely high amounts of greenhouse gases. However, new research shows that simply fencing and enhancing a dam can halve methane emissions.
In 2018 an unexpected discovery by Deakin's Blue Carbon Lab team found that farm dams emit significantly more greenhouse gases than lakes, reservoirs, and many natural freshwater systems.
These emissions are triggered by fertiliser and manure run-off, increasing nutrients and creating the ideal conditions to produce methane - a gas with 30-100 times greater warming potential than carbon dioxide. Nevertheless, these emissions are often ignored in national greenhouse gas inventories.
Deakin researcher Dr Martino Malerba has spent the last four years determined to show that farms can significantly reduce their carbon footprint through very simple management actions.
In their latest research, published in the prestigious journal Global Change Biology, Dr Malerba and Deakin's Blue Carbon Lab researchers collaborated with the Sustainable Farms team at The Australian National University and discovered that by fencing farm dams to prevent livestock access, reduced carbon emissions by fifty-six per cent.
"Our research spanned four hundred kilometres across south-eastern Australia," said Dr Malerba. "We compared thirty-three unfenced farms with thirty-one fenced farm dams - sites that are part of the Sustainable Farms dams study - and found the fenced dams produced fifty-six per cent less methane than unfenced.
"This is a huge difference and clearly shows that very simple management actions can drastically improve the dam water quality as well as decrease methane emissions, contributing to more productive and sustainable farming."
Fenced farm dams recorded thirty-two per cent less dissolved nitrogen, thirty-nine per cent less dissolved phosphorus, twenty-two per cent more dissolved oxygen, and produced fifty-six per cent less diffusive methane emissions than unfenced dams.
Surprisingly, this study found that farm dams with high dissolved oxygen can stop emitting methane and start absorbing greenhouse gases from the atmosphere. This means improving the condition of farm dams could turn these systems from carbon polluters to become a solution for mitigating the effects of climate change.
"These findings really should provide policymakers with the evidence needed to support dam enhancement," said Dr Malerba. "With the frequency of empty farm dams increasing two-to-five-fold since 1965, farmers are really doing it tough.
"We are working with the Clean Energy Regulator so that managing farm dams for avoided emissions could allow farmers to access financial incentives through carbon credits from the Emission Reduction Fund."
Dr Ben Scheele, from Sustainable Farms at The Australian National University, agreed:
"Our team has been investigating how farm dam management can be enhanced to improve water quality for livestock consumption, provide habitat for wildlife and provide more reliable water during droughts. The discovery that the same management practices that improve water quality and help wildlife also decrease greenhouse gas emissions is exciting and highlights the co-benefits associated with adapting sustainable management practices on farms."
